Mobile communication devices, such as mobile telephones provided with a camera are known. The mobile telephone has a camera which can capture an image of an object and a flash-light which can generate a light flash in order illuminate the object when the camera generates the image. The mobile telephone further has a transceiver which can transmit and receive radio signals. The transceiver is connected to a power source, a 1000 mAh lithium-based chemical battery, which provides power to the transceiver.
However, a disadvantage is that the light source and the transceiver can not operate simultaneously. The transceiver includes a power amplifier which uses about 1 A of current during peak operation, whereas the light source typically draws a peak current of 1 A from the battery during the flash. In case the peak current from the power amplifier and the light source occurs simultaneously, the battery has to deliver a current of several amperes during several milliseconds. This amount of current may cause a drop in the supply voltage due to the internal resistance of the battery, the resistance of the battery contacts and other resistances in the path between the battery and the electronic components in the phone, which could cause a crash of the software running on the mobile telephone.
Accordingly, to operate the light source and the transceiver simultaneously additional measures are required. A possible solution is to include ‘super’ capacitors in the transceiver to provide the amount of current required to operate the flash light and the transceiver simultaneously. However, a disadvantage is that capacitors occupy a large amount of space. Accordingly, the transceiver would be relatively large. Furthermore, in case the transceiver is implemented as an integrated circuit, the capacitors would increase the amount of substrate area required for the circuit. This increases the costs of the circuit significantly, since the substrate area is a significant factor in the costs of an integrated circuit. Also, the ‘super’ capacitors introduce complex mechanical constraints.